Rolf Mowatt-Larssen is paid to think about the unthinkable. As the Energy Department's director of intelligence, he's responsible for gathering information about the threat that a terrorist group will attack America with a nuclear weapon.

With his shock of white hair and piercing eyes, Mowatt-Larssen looks like a man who has seen a ghost. And when you listen to a version of the briefing he has been giving recently to President Bush and other top officials, you begin to understand why. He is convinced that al-Qaeda is trying to acquire a nuclear bomb that will leave the ultimate terrorist signature -- a mushroom cloud.

Ignatius then goes on to list a familiar list of mostly unverified or over-hyped claims.

As early as 1993, Osama bin Laden offered $1.5 million to buy uranium for a nuclear device, according to testimony presented in federal court in February 2001. When the al-Qaeda leader was asked in 1998 if he had nuclear or chemical weapons, he responded: "Acquiring weapons for the defense of Muslims is a religious duty. If I have indeed acquired these weapons, then I thank God for enabling me to do so."

Even as al-Qaeda was preparing to fly its airplane bombs into buildings, the group was also trying to acquire nuclear and biological capabilities. In August 2001, bin Laden and his deputy, Ayman al-Zawahiri, met around a campfire with Pakistani scientists from a group called Umma Tameer-E-Nau to discuss how al-Qaeda could build a nuclear device. Al-Qaeda also had an aggressive anthrax program that was discovered in December 2001 after bin Laden was driven from his haven in Afghanistan.

Al-Qaeda proclaimed a religious rationale to justify the WMD attacks it was planning. In June 2002, a Kuwaiti-born cleric named Suleiman Abu Ghaith posted a statement on the Internet saying that "al-Qaeda has the right to kill 4 million Americans" in retaliation for U.S. attacks against Muslims. And in May 2003, at the same time Saudi operatives of al-Qaeda were trying to buy three Russian nuclear bombs, a cleric named Nasir al-Fahd issued a fatwa titled "A Treatise on the Legal Status of Using Weapons of Mass Destruction Against Infidels." Interrogations of al-Qaeda operatives confirmed that the planning was serious. Al-Qaeda didn't yet have the materials for a WMD attack, but it wanted them.

Most chilling of all was Zawahiri's decision in March 2003 to cancel a cyanide attack in the New York subway system. He told the plotters to stand down because "we have something better in mind." What did that mean? More than four years later, we still don't know.

Merely repeating these claims, or painting them in the most sinister possible light, does not make a case that adds up to much of anything. We have to remember that virtually nothing we were told about al-Qaeda or Zarqawi or al-Qaeda in Iraq, or the intelligence we tortured out of people, has turned out to be true. Our intelligence has been gleaned from anti-Saddam forces, disgruntled alcoholic ex-patriots, forged documents...then cherry-picked and stove-piped through the normal intelligence vetting protocols. Zarqawi was largely a creation of the Pentagon.

At this point we really have no choice but to discard any intelligence that that is or has been leaked out of this administration. Where this a documented evidence, as in a pre-9/11 interview with bin-Laden, we need to remain calm and realize that he was boasting and bluffing. Remember, Saddam Hussein did the exact same thing by refusing to be absolutely clear and transparent that he had no WMD. He wanted some ambiguity as a deterrent to his neighbors and probably for us.

Al-Qaeda could conceivably buy a nuclear device but they cannot produce one on their own. Fortunately for humanity, it is very costly, complex, and time-consuming to create fissile material.

We should be concerned about any non-state actor getting nuclear material. The solution is complex, but it does not involve increasing our enemies' resolve to harm us. It does not involve eviscerating our privacy rights.

No state is going to give nuclear material to any entity that they cannot directly control. If Iran were to go through all the trouble to create a nuclear bomb, they would not give it to terrorists. Being a Shi'ite country, they certainly would not give it to Sunni terrorists. But if we attack them they might retaliate in the only way feasible for them. They might form their own terror cells as a delivery system.

This is all too hypothetical at this point to even warrant serious discussion. But think about it.

Iran cannot invade the United States and we rule the air and sea. They can do nothing outside of their immediate area. They might attack our troops in Iraq or Afghanistan...they might shut down the shipping lanes in the Straights of Hormuz. But if they were to attempt to attack us here, they would have to use stealth. The attack could not be traceable back to them. Yet, they could not trust non-Iranians to do the job if it entailed nuclear materials. In other words, the only way we might ever find ourselves at risk of a nuclear attack from Iran is if they felt they could carry it out without fingerprints. But Iran would never be able to carry it out without potential fingerprints.

Al Qaeda is never going to get nuclear materials from Iran. But they might get them from Pakistan, or on the Russian black market, or even someday from Saudi Arabia. But, again, no state would ever give that material away to someone they could not control. Only a failed nuclear state (as Russia sometimes resembled in the 1990's, and as Pakistan is at risk of becoming today) is a realistic source.

Ignatius serves up the fear...fear exquisitely timed to affect the FISA debate...but the fear is overblown. We must remain vigilant, but our best defense is a combination of stabilizing Pakistan, monitoring North Korea, improving relations with Russia, keeping Saudi Arabia non-nuclear, and, above all, not provoking people into wanting to attack us.

How to pull off both goals at the same time is a balancing act that we are currently failing on all fronts.